The invention relates to flow collection and distribution systems. One example of the many uses for such systems is in demineralizers where water to be used as boiler feed stock is treated by passing it downwardly in a vessel through a bed of deionizing resin beads which remove the minerals. The treated water or other fluid is typically collected at the bottom of the bed in a "Header-Lateral" comprising a parallel array of horizontal "lateral" perforated screens which branch out from a central manifold pipe or "header" to substantially cover the entire cross-section of the vessel.
In many applications, the screen system is used not only to collect treated fluid which has trickled down through the bed but also to distribute fluid, such as a dilute solution of H.sub.2 SO.sub.4, which percolates upward through the bed for regeneration purposes. Typically, each lateral consists of a pipe containing a plurality of drilled or cast holes in its wall which is installed within a cylindrical screen of the type commonly used in water wells. The number, location and size of the holes in the pipe determine the flow rate and the distribution for the incoming or outgoing fluid flow. The screen must, of course, have a mesh small enough to prevent the passage of the resin beads or other solid material to which the laterals are exposed.
Where preferred flow rates in either direction are generally identical, it is, of course, possible to provide appropriate outlet and inlet valves for alternatively connecting a particular header-lateral system to either a collection pipe or to a source of regeneration liquid. Where preferred flow rates are substantially different, such as the common situation where the regeneration flow rate is preferably far less than the collection rate, it is not possible to use the same system for both collection and distribution. This is so since it is desired that the regeneration liquid be uniformly dispersed at a uniform rate throughout the cross-section of the bed. Obviously, if one merely reduced the regenerant input flow rate in a system having holes sized for the greater flow rate required during collection, the flow would be greater through the holes closest to the liquid source than those further away if in fact any fluid reached the distant holes and the bed would not be uniformly regenerated.
One solution which achieves uniform collection and distribution is to place a distribution pipe system concentrically inside a collection pipe system with each system having holes sized for its intended flow rate. Another solution is to provide completely separate collection and distribution systems with each being sized for a particular flow rate. Obviously, these latter solutions are expensive. Furthermore, they consume a considerable amount of space in the bed and produce a certain amount of interference with flow. Where separate systems are used, there is a problem of being able to locate each on the bottom of the bed.